Campbell Scientific AM16-32A User Manual
AM16/32A Relay Multiplexer
Revision: 11/07
Copyright © 1987-2007
Campbell Scientific, Inc.
Warranty and Assistance
The AM16/32A RELAY MULTIPLEXER is warranted by CAMPBELL
SCIENTIFIC, INC. to be free from defects in materials and workmanship
under normal use and service for twelve (12) months from date of shipment
unless specified otherwise. Batteries have no warranty. CAMPBELL
SCIENTIFIC, INC.'s obligation under this warranty is limited to repairing or
replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products.
The customer shall assume all costs of removing, reinstalling, and shipping
defective products to CAMPBELL SCIENTIFIC, INC. CAMPBELL
SCIENTIFIC, INC. will return such products by surface carrier prepaid. This
warranty shall not apply to any CAMPBELL SCIENTIFIC, INC. products
which have been subjected to modification, misuse, neglect, accidents of
nature, or shipping damage. This warranty is in lieu of all other warranties,
expressed or implied, including warranties of merchantability or fitness for a
particular purpose. CAMPBELL SCIENTIFIC, INC. is not liable for special,
indirect, incidental, or consequential damages.
Products may not be returned without prior authorization. The following
act
information is for US and International customers residing in countries
cont
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company
serves your country. To obtain a Returned Materials Authorization (RMA),
contact CAMPBELL SCIENTIFIC, INC., phone (435) 753-2342. After an
applications engineer determines the nature of the problem, an RMA number
will be issued. Please write this number clearly on the outside of the shipping
container. CAMPBELL SCIENTIFIC's shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____
e
815 W
Logan, Utah 84321-1784
CAMPBELL SCIENTIFIC, INC. does not accept collect calls.
st 1800 North
AM16/32A Relay Multiplexer
Table of Contents
PDF viewers note: These page numbers refer to the printed version of this document. Use
the Adobe Acrobat® bookmarks tab for links to specific sections.
1. Function........................................................................1
1.1 Typical Applications.................................................................................1
1.2 Compatibility............................................................................................2
2. Physical Description ...................................................2
3. AM16/32A Specifications ............................................ 3
4. Operation......................................................................5
4.1 The Control Terminals..............................................................................5
4.1.1 Reset................................................................................................6
4.1.2 Clock...............................................................................................6
4.1.3 Ground............................................................................................7
4.1.4 Power Supply..................................................................................7
4.2 Measurement Terminals ...........................................................................8
4.2.1 COM Terminals..............................................................................9
4.2.2 Sensor Input Terminals...................................................................9
5. Datalogger Programming..........................................10
5.1 Single Loop Instruction Sequence..........................................................11
5.2 Multiple Loop Instruction Sequence.......................................................16
5.3 CRBasic Programming...........................................................................18
5.3.1 CR5000 and CR3000 Programming .............................................19
5.3.2 CR1000, CR800, and CR850 Programming.................................20
5.4 General Programming Considerations....................................................22
6. Sensor Hook-up and Measurement Examples........22
6.1 Single-Ended Analog Measurement without Sensor Excitation.............22
6.2 Differential Analog Measurement without Sensor Excitation................23
6.3 Half Bridge Measurements.....................................................................24
6.3.1 Half Bridge Measurement with Completion Resistor at
Datalogger ......................................................................................24
6.3.2 Potentiometer Measurement..........................................................25
6.3.3 Four Wire Half Bridge (Measured Excitation Current).................25
6.4 Full Bridge Measurements......................................................................26
6.5 Full Bridges with Excitation Compensation...........................................27
i
AM16/32A Relay Multiplexer Table of Contents
6.6 Thermocouple Measurement.................................................................. 28
6.6.1 Measurement Considerations....................................................... 28
6.6.2 Single-ended Thermocouple Measurement.................................. 30
6.6.3 Differential Thermocouple Measurement .................................... 31
6.7 Mixed Sensor Types............................................................................... 31
6.7.1 Mixed Sensor Example: Soil Moisture Blocks and
Thermocouples............................................................................... 31
7. General Measurement Considerations ....................35
8. Installation..................................................................35
8.1 Mounting Tabs....................................................................................... 36
8.2 Controlling Humidity............................................................................. 36
Appendices
A. AM16/32A Improvements........................................A-1
Figures
1. AM16/32A Relay Multiplexer................................................................... 3
2. AM16/32A Relay Actuation Time vs. Temperature and Battery Voltage.. 5
3. AM16/32A to Datalogger Power/Control Hookup.................................... 6
4. Power and Ground Connections for External Power Supply..................... 8
5. Typical AM16/32A to Datalogger Signal Hookup (4x16 Mode)...............9
6. SCWIN (Short Cut for Windows Program Builder) ................................ 10
7. Example “4x16” Mode Program Loops for CR23X, CR10(X),
21X, and CR7 Dataloggers............................................................ 14
8. Example “2x32” Mode Program Loops for CR23X, CR10(X),
21X, and CR7 Dataloggers............................................................ 15
9. Wiring Diagram for Strain Gages and Potentiometers............................. 16
10. Single-ended Measurement without Excitation......................................23
11. Differential Measurement without Excitation........................................ 23
12. Half Bridge (Modified 107 Temperature Probe) Hook-up and
Measurement.................................................................................. 24
13. Potentiometer Hook-up and Measurement............................................. 25
14. Four Wire Half Bridge Hook-up and Measurement............................... 26
15. Full Bridge Measurement....................................................................... 26
16. Full Bridge Measurement with Excitation Compensation..................... 27
17. Differential Thermocouple Measurement with Reference
Junction at the Datalogger ............................................................. 29
18. Differential Thermocouple Measurement with Reference
Junction at the AM16/32A............................................................. 29
19. AM16/32A Aluminum Cover Plate....................................................... 30
20. Thermocouple and Soil Block Measurement......................................... 32
21. Mounting Tab Hole Pattern.................................................................... 36
ii
Cautionary Notes
The AM16/32A is not designed to multiplex power. Its intended function is to
switch low level analog signals. Switched currents in excess of 30 mA will
degrade the relay contacts involved, rendering that channel unsuitable for
further low level analog measurement. Customers who need to switch power
are directed to Campbell Scientific’s SDM-CD16AC, A6REL-12, or
A21REL-12 relays.
Changing the setting of the mode switch from “4x16” to “2x32” connects
COM ODD H to COM EVEN H and also COM ODD L to COM EVEN L.
After wiring AM16/32A, exercise due care to avoid inadvertently putting
excess voltage on a line or short circuiting a power supply which might
damage datalogger, wiring panel, sensor or multiplexer (not covered under
warranty).
iii
This is a blank page.
AM16/32A Relay Analog Multiplexer
1. Function
The primary function of the AM16/32A Multiplexer is to increase th e number
of sensors that can be measured by a CR1000, CR3000, CR800, CR850,
CR23X, CR10(X), 21X, or CR7 datalogger. The AM16/32A is positioned
between the sensors and the datalogger. The AM16/32A is a replacement for
CSI’s AM16/32 model. Mechanical relays in the AM16/32A connect each of
the sensor channels in turn to a common output destined for the datalogger.
The user program advances the multiplexer through the sensor channels
making measurements and storing data.
A slide switch located on the AM16/32A’s top panel selects one of two modes
of operation. In “2x32” mode the multiplexer can scan 32 sensor input
channels, each with two lines. In “4x16” mode it can scan 16 input channels
with four lines a piece. The datalogger program is written according to the
selected mode and the sensors to be measured.
The maximum number of sensors that can be multiplexed by an AM16/32A
depends primarily on the type(s) of sensors to be scanned. The following
guidelines assume identical sensors:
Up to 32 single-ended or differential analog sensors that do not require
excitation. For example: pyranometers and thermocouples (see Sections 6.1,
6.2, and 6.6).
Up to 32 single-ended sensors that require excitation. Example: some half
bridges (see Section 6.3.1).
Up to 16 single-ended or differential sensors that require excitation.
Examples: full bridges and four-wire half bridge with measured excitation (see
Section 6.3.3 and 6.4).
In conjunction with a second AM16/32A, up to 16 six-wire full bridges
(Section 6.5).
1.1 Typical Applications
The AM16/32A is intended for use in applications where the number of
required sensors exceeds the number of datalogger input channels. Most
commonly, the AM16/32A is used to multiplex analog sensor signals, although
it can also be used to multiplex switched excitations, continuous analog
outputs, or even certain pulse counting measurements (i.e., those that require
only intermittent sampling). It is also possible to multiplex sensors of
different, but compatible, types (e.g., thermocouples and soil moisture blocks,
see Section 6.7.1).
1
AM16/32A Relay Analog Multiplexer
NOTE
For a discussion of single-ended versus differential analog
measurements, please consult the Measurement section of your
datalogger manual.
As purchased, the AM16/32A is intended for use in indoor, non-condensing
environments. An enclosure is required for field or high humidity use. In
applications where one or two multiplexers are deployed, the ENC 10/12
(10” x 12”) enclosure is recommended.
1.2 Compatibility
The AM16/32A is compatible with Campbell’s CR5000, CR800, CR850,
CR3000, CR1000, CR23X, CR10(X), 21X, and CR7 dataloggers.
The AM16/32A is compatible with a wide variety of commercially available
sensors. As long as relay contact current maximums are not exceeded (see
Cautionary Notes, page iii), and no more than four lines are switched at a time,
system compatibility for a specific sensor is determined by sensor-datalogger
compatibility.
In CR1000, CR800, CR850, CR3000, CR23X, and CR10(X) applications the
AM16/32A may be used to multiplex up to 16 Geokon vibrating wire sensors
through one AVW1 vibrating wire interface.
2. Physical Description
The AM16/32A is housed in a 10.2 cm x 23.9 cm x 4.6 cm (4.0” x 9.4” x 1.8”)
anodized aluminum case (Figure 1). The aluminum case is intended to reduce
temperature gradients across the AM16/32A’s terminal strips. An aluminum
cover plate is also included to this end. This is extremely important if
thermocouples are being multiplexed (Section 6.6).
The case can be opened for inspection/cleaning by removing two phillips-head
screws located on the under-side of the case. Mounting tabs are provided so
the AM16/32A can be fastened to a flat surface or an enclosure plate (Section
8).
All connections to the AM16/32A are made on the top panel terminal blocks.
The island of four terminals located near the mode switch are dedicated to the
connecting of datalogger power and control lines (Section 4.1). The four
“ODD” and “EVEN” “COM” terminals on the other side of the mode switch
carry shielded multiplexed sensor signals destined for datalogger analog
inputs. The remaining terminals on the AM16/32A are for sensor and sensor
shield connection (Section 4.2). All of the inputs of the AM16/32A are
protected with gas tubes. The terminals accept stripped and tinned lead wires
up to 16 AWG or 1.6 mm in diameter. Datalogger-to-AM16/32A cabling
requires a minimum of six and as many as nine individually insulated wires
with shields.
2
FIGURE 1. AM16/32A Relay Multiplexer
3. AM16/32A Specifications
AM16/32A Relay Analog Multiplexer
Power*:
Current Drain:
Reset*:
Clock*:
Operational
Temperature:
Operational
Humidity:
Unregulated 12 VDC
Minimum Operating Voltage:
from –55C to +40C = 11.3 VDC;
from +40C to +85C = 11.8 VDC
(See Figure 2 for relay actuation times vs.
temperature and supply voltage.)
Quiescent: < 210 uA
Active: 6 mA typical in “2 x 32” mode
11 mA typical in “4 x 16” mode
A continuous signal between 3.5 VDC and 16 VDC
holds the AM16/32A in an active state (where a
clock pulse can trigger a channel advance). A
signal voltage < 0.9VDC deactivates the
AM16/32A (clock pulse will not trigger a scan
advance; AM16/32A is also reset).
On the transition from <1.5 V to >3.5 V, a scan
advance is actuated on the leading edge of the clock
signal; clock pulse should be a minimum of 1 ms
wide.
Standard: -25oC to +50oC
Extended: -55oC to +85oC
0 - 95%, non-condensing
3
AM16/32A Relay Analog Multiplexer
Dimensions:
Length – 23.9 cm (9.4")
Width - 10.2 cm (4.0")
Depth - 4.6 cm (1.8")
Weight:
Mounting Tab
Hole Spacing:
Expandability
**
(nominal):
Maximum Cable
Length:
Maximum Switching
Current
***
:
Contact
Specifications:
1.5 lbs. (approx.), 693 g.
1 inch x 3 inches x 9 inches. Up to 1/8 inch or 3
mm diameter screws (see Figure 21).
2 AM16/32As per CR800/CR850
4 AM16/32As per CR3000
4 AM16/32As per CR5000
4 AM16/32As per CR1000
4 AM16/32As per CR23X
4 AM16/32As per CR10(X)
4 AM16/32As per 21X
8 AM16/32As per CR7 725 Card
Depends on sensor and scan rate. In general, longer
lead lengths necessitate longer measurement delays.
Refer to datalogger manual for details.
500 mA
Initial contact resistance: <0.1 ohm max.
Initial contact bounce: <1 ms
Contact material: Gold clad silver alloy
Wiper to N.O. contact capacitance: 0.5 pF
Typical low-current (<30 mA) life: 5 x 10
7
operations
Relay Switching
Characteristics
(applying 11.3 – 14
VDC):
ESD:
Thermal emf: 0.3 µV typical; 0.5 µV maximum
Operate time: <10 ms over temperature and supply
ranges
Break before make guaranteed by design
Air Discharge: complies with IEC61000-4-2, test
level 4 (±15 kV)
Contact Discharge: complies with IEC61000-4-2,
test level 4 (±8 kV)
Surge:
Complies with IEC61000-4-5, test level 3 (±2 kV,
2 ohms coupling impedance)
*
Reset, Clock, and +12V inputs are protected by +16V transzorbs.
**
Assumes sequential activation of multiplexers and that each datalogger channel is uniquely
dedicated. If your application requires additional multiplexing capability, please consult CSI for
application assistance.
***
Switching currents greater than 30 mA (occasional 50 mA current is acceptable) will degrade
the contact surfaces of the mechanical relays (increase their resistance). This will adversely affect
the suitability of these relays to multiplex low voltage signals. Although a relay used in this
manner no longer qualifies for low voltage measurem ent, it continues to be useful for switching
currents in excess of 30 mA.
4
AM16/32A Relay Analog Multiplexer
12.0
10.0
8.0
6.0
4.0
2.0
RELAY ACTUATION TIME (ms)
0.0
10
9.6
10.4
10.8
11.2
11.61212.4
POWER SUPPLY VOLTAGE
65C
12.8
13.2
13.61414.4
50C
14.8
25C
15.2
-25C
16
15.6
FIGURE 2. AM16/32A Relay Actuation Time vs.
Temperature and Battery Voltage.
4. Operation
4.1. The Control Terminals
Subsection 4.1 discusses the terminals that control operation of the
multiplexer. These terminals are located at the left-hand side of the
multiplexer as shown in Figure 1. Subsection 4.2 d iscusses the use of sensor
measurement terminals.
The CR5000, CR3000, CR800, CR850, CR1000, CR23X, CR10(X), 21X, and
CR7 dataloggers connect to the AM16/32A as shown in Figure 3 (“4x16”
mode). Figure 3 depicts control connections. Measurement connections are
discussed in Section 6. The power, ground, reset, and clock connections
remain essentially the same regardless of datalogger used.
With the CR5000, CR3000, CR800, CR850, CR1000, CR23X and CR10(X)
the datalogger 12 VDC supply and ground terminals are connected to the
AM16/32A 12V and ground terminals. One control port is required for
clocking and a second control port for reset. The MUXPOWER cable (or
equivalent) shield is grounded on both ends as illustrated below.
5
AM16/32A Relay Analog Multiplexer
RES
CLK
GND
12V
O
N
CR23X,
CR5000
21X
MUXPOWER
SHIELD
CR10X,
CR800,
CR850
G G
12 V 12 V 12 V +12 V 12 V
G G G
C1-C4 C1-C8 C1-C8 EXCIT 1-4 EXCITATION
C1-C4 C1-C8 C1-C8 C1-C8 725 Card
CR3000,
CR1000
FIGURE 3. AM16/32A to Datalogger Power/Control Hookup
With the 21X or CR7 the AM16/32A connects to the 12 VDC and “
terminals for power. One control port is used for reset, and one switched
excitation channel is used for clock (on 725 card with CR7). If a switched
excitation port is not available, an additional control port can be used to
provide clock pulses to the multiplexer.
CR7
Control
”
4.1.1 Reset
4.1.2 Clock
The reset (“RES”) line is used to activate the AM16/32A. A signal in the
range of +3.5 to +16 VDC applied to the reset terminal activates the
multiplexer. When this line drops lower than +0.9 VDC, the multiplexer
enters a quiescent, low-current-drain state. In the quiescent state the common
(“COM”) terminals are electrically disconnected from all of the sensor input
channels. Reset should always connect to a datalogger control port. Instruction
86 (option code 41 - 48 to activate, and 51 - 58 to deactivate) is generally used
to activate/deactivate the multiplexer, however, in the case of the 21X or CR7
with older PROMS, Instruction 20 is commonly used. The CR800, CR850,
CR3000, CR5000, and CR1000 uses the PortSet instruction to control the reset
line.
Pulsing the AM16/32A “CLK” line high (“RES” line already high) advances
the channel. When reset first goes high, the common terminals ODD H,
ODD L and EVEN H, EVEN L are disconnected from all sensor input
terminals. With the panel switch in “4x16” mode, when the first clock pulse
arrives the “COM” terminals are switched to connect with sensor input channel
1 (blue lettering) consisting of 1H, 1L, 2H, and 2L. When a second clock
pulse arrives the common lines are switched to connect to channel 2 (3H, 3L,
4H, 4L). The multiplexer advances on the leading edge of the positive going
clock pulse. The voltage level must fall below 1.5 VDC and then rise above
3.5 VDC to clock the multiplexer. The CLK pulse should be at least 1 ms
long. A delay (typically 10 to 20 ms) is inserted between the beginning of the
CLK pulse and the measurement instruction to ensure sufficient settling time
for relay contacts.
6
4.1.3 Ground
AM16/32A Relay Analog Multiplexer
With the 21X and CR7 dataloggers, switched excitation is generally used to
clock the multiplexer (Instruction 22 configured for 5000 mV excitation). If
no switched excitation channel is available, it is possible to clock using control
ports. See Section 5.1 for details.
In the case of the CR5000, CR3000, CR800, CR850, CR1000, CR23X, and
CR10(X), a control port is generally used to clock the multiplexer. Instruction
86 with the pulse port option (command code 71 through 78) generates a 10 ms
pulse which works well.
The CR5000, CR3000, CR800, CR850, and CR1000 uses a control port
controlled by PortSet, Delay, and SubScan/NextSubScan to create the Clock
pulses (see program example in Section 5.3).
If several multiplexers are required, a CR5000, CR3000, CR800, CR850,
CR1000, CR10(X) or CR23X control port can source sufficient current to
drive up to six AM16/32A CLK or RES inputs wired in parallel.
The AM16/32A has a ground lug that should be connected to earth ground via
an 8 AWG wire. This connection should be as short as possible.
The AM16/32A “GND” terminal is connected to datalogger power ground.
The AM16/32A “GND” terminal is also connected to the MUXPOWER cable
(or equivalent) SHIELD and, via that, to datalogger power ground (see Figure
3). If a separate power supply is used, the AM16/32A ground should also
connect to the separate supply’s ground (Figure 4). An AM16/32A
“COM
“G”) via the MUXSIGNAL cable (or equivalent) also according to Figure 5
(see 4.2.1). The datalogger itself must connect to earth ground by one of the
methods described in the Installation and Maintenance Section of your
datalogger operator’s manual.
4.1.4 Power Supply
The AM16/32A requires a continuous 12 VDC power supply for operation.
The multiplexer's current drain is less than 210 microamps in the quiescent
state and is typically 6 to 11 milliamps at 12 VDC when active (see current
drain spec). The power supply is connected to the multiplexer terminals
labeled “12V” (+) and “GND”. Connect the “GND” wire first for safety.
In many applications it is convenient to power the AM16/32A from a
datalogger battery. For more power-intensive applications, an external,
rechargeable, 12 VDC, 60 Amp Hr source may be advisable. Lead-acid
supplies are recommended where solar or AC charging sources are available
because they handle well being “topped off” by constant charging. The
BPALK alkaline supply (12 Amp Hr) can be used to power the AM16/32A in
applications where the average system current is low, or where it is convenient
to frequently replace batteries. It is advisable to calculate the total power
requirements of a system and the expected longevity of the power supply based
on average system current drains (e.g. logger, multiplexer, other peripherals
and sensors) at the expected ambient temperatures.
” terminal should connect to a datalogger ground terminal (“
” or
7
AM16/32A Relay Analog Multiplexer
The average power required to operate an AM16/32A depends on the
percentage of time it is active per time period. For example, if a CR10X
makes differential measurements on 32 thermocouples every minute, the
average current drain due to the AM16/32A would be about ((.030 Sec/chan x
32 chan)/60 Sec) x 6 mA = 0.1 mA. Under the same conditions, a 2 second
execution interval rate increases the average system current drain to about
((.030 Sec/chan x 32 chan)/2 Sec) x 6 mA = 2.9 mA. At a minimum, the
power supply must be able to sustain the system between site visits anticipating
the worst environmental extremes.
If a 21X power supply is used to power the AM16/32A, all low-level analog
measurements (thermocouples, pyranometers, thermopiles, etc.) must be made
differentially. Differential measurements are required because slight ground
potentials are created along the 21X analog terminal strip when the 12V supply
is used to power peripherals. This limitation reduces the number of available
analog input channels and may mandate the use of an external supply for the
AM16/32A (Figure 4).
FIGURE 4. Power and Ground Connections for External Power Supply.
Low supply voltage and high ambient temperatures affect the actuation time of
the multiplexer relays (Figure 2). If your program does not allow the relay
contacts sufficient time to close before a measurement is started, the result will
be inaccurate or overranged values.
4.2 Measurement Terminals
Most of the terminals on the AM16/32A are dedicated to the connection of
sensors to the multiplexer (Figure 1). Depending on the panel switch selection
(“4x16” or “2x32” mode), the sensor input terminals are organized into 16
groups (blue letters) of 4 sensor inputs or 32 groups (white letters) of 2 sensor
inputs. The terminals accept solid or tinned, stripped sensor leads. The four
“COM” terminals marked “ODD H, L” and “EVEN H, L” located by the mode
switch provide for attachment of the common signal leads that carry
multiplexed sensor signals to the datalogger.
8
Loading...